Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A cellular wireless network may include a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless communication devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
Such a cellular wireless network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to WCDs defining a downlink or forward link and communications from the WCDs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Code Division Multiple Access (CDMA) (e.g., 1xRTT and 1xEV-DO), Long Term Evolution (LTE), WiMAX, iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, MMDS, WIFI, and BLUETOOTH. Each protocol may define its own procedures for registration of WCDs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies and may define a number of air interface channels for carrying information between the base station and WCDs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing for instance.
By way of example, each coverage area may define a pilot channel, reference channel or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that WCDs may detect as an indication of coverage and may measure to evaluate coverage strength. As another example, each coverage area may define one or more uplink control channels or other resources on which WCDs may transmit control messages to the base station. And each coverage area may define one or more downlink control channels or other resources on which the base station may transmit control messages to WCDs. Each coverage area may then define one or more traffic channels or other resource for carrying communication traffic such as voice data and other data between the base station and WCDs.
When a WCD first powers on or enters into coverage of the network, the WCD may scan for and identify a strongest pilot or reference signal (e.g., having the highest signal-to-noise ratio) and may register with the network by transmitting a registration request or attach request to a base station providing that signal. This registration process may serve to notify the network of the WCD's presence in a particular coverage area and to facilitate network authentication of the WCD. Once registered, the WCD may then operate in an idle mode (i.e., the WCD may idle in the selected coverage area) in which the WCD monitors a downlink control channel to receive overhead information and to check for any page messages. In the idle mode, the WCD may have no assigned traffic channel resources on which to engage in bearer communication.
Further, when the WCD is operating in the idle mode, the WCD may continue to regularly scan pilot or reference signals, from both the coverage area in which the WCD is idling and any other coverage areas that extend to the WCD's location. Through this process, if the WCD thereby detects that another coverage area is stronger than the coverage area in which the WCD is idling, the WCD may then transition to idle in that other coverage area instead, i.e., the WCD may engage in idle handoff to the other coverage area. In addition, depending on the circumstances, the WCD may also then re-register with the network, to notify the network of the WCD's presence in the new coverage area.
When the network has a communication (such as a voice call or other traffic) to provide to a WCD that is registered with the network but is operating in the idle mode, the network may page the WCD in an effort to then facilitate assigning traffic channel resources to the WCD. In particular, the network may transmit a page message to the WCD on a downlink paging channel. Assuming the WCD receives this page message, the WCD may then transmit a page response message to the network on an uplink access channel. And upon receipt of the page response message, the network may then assign traffic channel resources to the WCD, for use to carry the communication, thus transitioning the WCD to a connected or active mode in which the WCD can engage in the communication.
Likewise, when an idle WCD seeks to initiate a communication (such as to place a voice call or engage in other bearer communication), the WCD may transmit on an uplink access channel to the base station a connection request (e.g., origination request), and the network may then assign traffic channel resources to the WCD for use to carry the communication, similarly transitioning the WCD to a connected or active mode in which the WCD can engage in the communication.